Method for controlling unidirectional link connection in mobile ad hoc networks and recording medium storing program thereof

ABSTRACT

Disclosed is a method for controlling unidirectional link connection in a mobile ad hoc network which comprises: mobile nodes including transmission power information in a beacon message that is periodically transmitted; using the information to sense a unidirectional link and maintain residual power information with regard to the corresponding node, and providing unidirectional link connectivity in the link layer to an upper layer through a filtering process using broadcasting and residual power information. Hence, the unidirectional links generated in the mobile ad hoc network may be accurately sensed using transmission power loss on a transmission path, and the frames generated in the link layer in the reverse direction of the unidirectional links may be transmitted.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based on Korea Patent Application No.2002-82860 filed on Dec. 23, 2002 in the Korean Intellectual PropertyOffice, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] (a) Field of the Invention

[0003] The present invention relates to a method for controllingunidirectional link connection in a mobile ad hoc network, and arecording medium storing a program thereof. More specifically, thepresent invention relates to a method for controlling unidirectionallink connection in a mobile ad hoc network, and a recording mediumstoring a program thereof for detecting unidirectional links generatedby a transmission power difference, and providing connectivity of aunidirectional link to an upper layer.

[0004] (b) Description of the Related Art

[0005] Ad hoc networks represent networks with only mobile terminals,designed in the assumption that most wireless MAC (medium accesscontrol) protocols have identical transmission power at all mobilenodes.

[0006] However, the actual ad hoc network includes various devicescategorized as battery-based personal portable devices, and devices thatare supplied with optimal power from their power source. The personalportable devices include a notebook computer, a PDA, and a mobile phone,and the devices receiving optimal power include mobile communicationdevices attached to tanks, helicopters, armored motorcars, fire engines,and ambulances.

[0007] The devices have different transmission powers because ofdifferences in power supplied to the devices and differences in size ofthe devices because of portability, which generates unidirectionallinks. Here, a unidirectional link may be generated between a hightransmission power node and a low transmission power node, wherein datais only transmitted from the high transmission power node to the lowtransmission power node.

[0008] So as to utilize the unidirectional link, the low transmissionpower node conventionally senses the unidirectional link, and a framethat approaches a start mobile node of the unidirectional link istunneled using a routing function of a network layer.

[0009] A method for sensing the unidirectional link according to priorart enables each mobile node to hold a neighbor node list of theneighboring nodes that are adjacent to the mobile node, load theneighboring node list into the ‘Hello’ message that is periodicallybroadcasted to adjacent neighboring nodes, and transmit the message tothe adjacent neighboring nodes.

[0010] In this instance, when the ‘Hello’ message is transmitted betweentwo mobile nodes in the unidirectional link relation, the neighboringnode list in the ‘Hello’ message of the high transmission power nodeincludes no low transmission power nodes.

[0011] Therefore, the low transmission power node is required to receivethe ‘Hello’ message and detect a unidirectional link. The lowtransmission power node uses information collected by a routing protocolto tunnel an ACK of a link layer from an end point of the unidirectionallink to the packet start point, and routing information of a networklayer. Accordingly, the high transmission power node may transmit datausing the unidirectional link.

[0012] As described above, since the prior art method for sensing theunidirectional link performs communication using the routing function ofan upper layer, it delays frame transmission and generates processingoverhead.

SUMMARY OF THE INVENTION

[0013] It is an object of the present invention to provide a method forcontrolling unidirectional link connection in an ad hoc network, and arecording medium for storing a program thereof for providingunidirectional link connectivity in the ad hoc network to an upper layerfrom a link layer.

[0014] In one aspect of the present invention, a method for controllingunidirectional link connection in a mobile ad hoc network comprises: (a)each mobile node sensing a unidirectional link when a unidirectionallink is generated because of a difference between transmission powers,the mobile nodes forming a mobile ad hoc network; (b) relaying a framegenerated in a link layer in the reverse direction of the unidirectionallink when the unidirectional link is sensed in (a); and (c) removing therepeated frame relay from among the relayed frames in (b), and providingunidirectional link connectivity in the link layer to an upper layer.

[0015] Sensing a unidirectional link in (a) comprises: (i) each mobilenode including transmission power and minimum receipt power informationin the frame and periodically transmitting them; (ii) receiving theframe transmitted in (i), and calculating path loss power on atransmission path and residual power; and (iii) sensing a unidirectionallink when transmission power is less than the summation of the path losspower calculated in (ii) and the minimum receipt power.

[0016] An address field of the frame transmitted in (i) includes a startaddress, a destination address, a recipient address, and a transmitteraddress.

[0017] In the address field of the frame, the start address includes amobile node with low transmission power, the destination addressincludes a mobile node with high transmission power, the recipientaddress includes a broadcast address, and the transmitter addressincludes an address of a mobile node for transmitting the correspondingframe.

[0018] In another aspect of the present invention, a recording mediumstores a program including functions comprising: each mobile nodesensing a unidirectional link when a unidirectional link is generatedbecause of a difference between transmission powers, the mobile nodesforming a mobile ad hoc network; relaying a frame generated in a linklayer in the reverse direction of the unidirectional link when theunidirectional link is sensed; and removing the repeated frame relayfrom among the relayed frames, and providing unidirectional linkconnectivity in the link layer to an upper layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate an embodiment of theinvention, and, together with the description, serve to explain theprinciples of the invention:

[0020]FIG. 1 shows a mobile ad hoc network for generating aunidirectional link caused by a transmission power difference;

[0021]FIG. 2 shows a process for transmitting a frame in the reversedirection of the unidirectional link generated in FIG. 1;

[0022]FIG. 3 shows an address field variation process of a frame whenthe frame is transmitted in the reverse direction of the unidirectionallink in a method for controlling the unidirectional link connection in amobile ad hoc network according to a preferred embodiment of the presentinvention; and

[0023]FIG. 4 shows a flowchart of the method for controlling theunidirectional link connection in a mobile ad hoc network according to apreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In the following detailed description, only the preferredembodiment of the invention has been shown and described, simply by wayof illustration of the best mode contemplated by the inventor(s) ofcarrying out the invention. As will be realized, the invention iscapable of modification in various obvious respects, all withoutdeparting from the invention. Accordingly, the drawings and descriptionare to be regarded as illustrative in nature, and not restrictive.

[0025]FIG. 1 shows a mobile ad hoc network for generating aunidirectional link caused by a transmission power difference.

[0026] As shown, a unidirectional link 130 is generated because of adifference between a transmission range 110 of a mobile node A and atransmission range 111 of other mobile nodes B through F.

[0027] In this instance, the mobile node A may transmit frames to themobile node F, but the mobile node F is not able to transmit framesdirectly to the mobile node A.

[0028]FIG. 2 shows a process for transmitting a frame in the reversedirection of the unidirectional link generated in FIG. 1.

[0029] Referring to FIG. 2, mobile nodes HPa and HPb with hightransmission powers each have a transmission range R, and mobile nodesLPa through LPg with low transmission powers each have a transmissionrange r.

[0030] As shown in FIG. 2, a unidirectional link is generated betweenthe mobile nodes HPa and LPc, and the frame transmitted to HPa from LPcis applied to all mobile nodes within the transmission range of LPc.

[0031] After receiving the frame from LPc, each mobile node processesthe frame to send it on a path to HPa when the frame is transmitted inthe reverse direction of the unidirectional link.

[0032] In the above, the frame transmitted by the LPc is transmitted tothe destination HPa in a converged format. If the mobile node HPb isprovided, the transmission path of the frame is in the order of LPc,HPb, and HPa; and if HPb is not provided, the transmission path is inthe order of LPc, LPb, Lpa, and HPa.

[0033]FIG. 3 shows an address field variation process of a frame whenthe frame is transmitted in the reverse direction of the unidirectionallink in a method for controlling the unidirectional link connection in amobile ad hoc network according to a preferred embodiment of the presentinvention.

[0034]FIG. 3 shows an address field variation process of the frame whenthe frame is transmitted through the path in order of LPc, LPb, LPa, andHPa in the case HPb is not provided.

[0035] When the mobile node HPa transmits data or a control message 250together with transmission TX power to the mobile node LPc, LPc senses aunidirectional link because of a transmission power difference betweenLPc and HPa.

[0036] In an address field 251 of the frame transmitted to LPb from LPc,a start address (SA) is LPc, a destination address (DA) is HPa, arecipient address (RA) is a broadcast address (BA), and a transmitteraddress (TA) is LPc when the frame is transmitted through the path inorder of LPc, LPb, LPa, and HPa.

[0037] In this instance, the SA and the DA are not modified during frametransmission, the RA is always set as the BA, and the TA is set as anaddress of a mobile node transmitting the corresponding frame.

[0038] Therefore, an address field 252 of the frame transmitted to LPafrom LPb and an address field 253 of the frame transmitted to HPa fromLPa have identical SA, DA, and RA, and TA is respectively modified toLPb and LPa.

[0039]FIG. 4 shows a flowchart of the method for controlling theunidirectional link connection in a mobile ad hoc network according to apreferred embodiment of the present invention.

[0040] As shown, a corresponding frame is received in step S1 when an RAof the frame transmitted by each mobile node is a BA or an address ofthe corresponding mobile node. When receiving a beacon message includingtransmission power and minimum receipt power after receiving theabove-noted frame, the mobile node calculates an SA of the frame,transmission path loss of a generated link, and residual power, and addsthe calculation results to a storage unit 300 and updates the same insteps S2 and S3.

[0041] A mobile node uses transmission power information included in thebeacon message to sense a unidirectional link and to maintain residualpower information to a corresponding mobile node. That is, the mobilenode senses it to be a unidirectional link when the transmission poweris less than the summation of path loss power and minimum receipt power.

[0042] The storage unit 300 stores added and updated information in asoftware format and deletes it when a predetermined time period haspassed.

[0043] When not receiving a beacon message, the mobile node determinesin steps S2 and S4 whether a relay request field is set in the frame.When the relay request field is set in the frame, the mobile nodedetermines in step S5 whether the destination of the frame is includedin the neighboring node list.

[0044] When the relay request frame is not set in the frame, or thedestination of the frame is included in the neighboring node list, themobile node performs a process identical with that of the frame, andterminates the corresponding process.

[0045] When the relay request frame is set in the frame, and thedestination is not included in the neighboring node list, the mobilenode determines in steps S5 and S6 whether residual power informationwith regard to the destination of the frame is provided.

[0046] In the above, when the residual power information is provided,the mobile node determines in step S7 whether stored residual power isgreater than the residual power included in the corresponding frame.

[0047] When the stored residual power is greater than the residual powerincluded in the corresponding frame, the mobile node updates the frame'sTA field and residual power information in step S8.

[0048] The case for LPb to receive the frame transmitted by LPc as shownin FIG. 2 is described as an exemplified case for updating the frame'sTA field and residual power information in the previous step S8.

[0049] When the frame's TA field and residual power information isupdated, the mobile node reflects residual power information to ageneration of back-off time before transmitting the corresponding framein step S9.

[0050] Hence, the mobile node transmits the frame so as to relay theframe to a mobile node that may closely transmit the corresponding frameto the destination of the frame in the shortest time in step S10.

[0051] When residual power information with regard to the frame'sdestination is not provided, or the residual power stored in the mobilenode is less than the residual power in the frame, the correspondingframe is deleted in step S11, thereby removing the frame repeatedbecause of failing to sense a unidirectional link, and minimizingtransmission power loss.

[0052] The case for LPd to receive the frame relayed by LPa duringrelaying of the corresponding frame when LPg receives the frametransmitted to HPa by LPc as shown in FIG. 2 is provided as an exemplarycase for deleting the repeated frame in the previous step S11.

[0053] According to the method for controlling unidirectional linkconnection in a mobile ad hoc network, and a recording medium storing aprogram thereof, the unidirectional links generated in the mobile ad hocnetwork are accurately sensed by using transmission power loss on thetransmission path.

[0054] Also, the method for controlling unidirectional link connectionin a mobile ad hoc network, and a recording medium storing a programthereof may transmit frames generated in the link layer in the reversedirection of the unidirectional link, remove repeated frames wastedbecause of failing to sense the unidirectional links in the prior art,and solve inefficient resource usage problems caused by link failureeven when the unidirectional link is generated.

[0055] Further, since the method for controlling unidirectional linkconnection in a mobile ad hoc network, and a recording medium storing aprogram thereof independently provide unidirectional link connectivityto an upper layer from the link layer, it is not affected by the upperlayer.

[0056] While this invention has been described in connection with whatis presently considered to be the most practical and preferredembodiment, it is to be understood that the invention is not limited tothe disclosed embodiments, but, on the contrary, is intended to covervarious modifications and equivalent arrangements included within thespirit and scope of the appended claims.

What is claimed is:
 1. A method for controlling unidirectional linkconnection in a mobile ad hoc network comprising: (a) each mobile nodesensing a unidirectional link when a unidirectional link is generatedbecause of a difference between transmission powers, the mobile nodesforming a mobile ad hoc network; (b) relaying a frame generated in alink layer in the reverse direction of the unidirectional link when theunidirectional link is sensed in (a); and (c) removing the repeatedframe relay from among the relayed frames in (b), and providingunidirectional link connectivity in the link layer to an upper layer. 2.The method of claim 1, wherein sensing a unidirectional link in (a)comprises: (i) each mobile node including transmission power and minimumreceipt power information in the frame and periodically transmittingthem; (ii) receiving the frame transmitted in (i), and calculating pathloss power generated on a transmission path, and residual power; and(iii) sensing a unidirectional link when transmission power is less thanthe summation of the path loss power calculated in (ii) and the minimumreceipt power.
 3. The method of claim 2, wherein an address field of theframe transmitted in (i) includes a start address, a destinationaddress, a recipient address, and a transmitter address.
 4. The methodof claim 3, wherein, in the address field of the frame, the startaddress includes a mobile node with low transmission power, thedestination address includes a mobile node with high transmission power,the recipient address includes a broadcast address, and the transmitteraddress includes an address of a mobile node transmitting thecorresponding frame.
 5. The method of claim 3, wherein, in the addressfield of the frame, the start address and the destination address arenot modified during frame transmission.
 6. The method of claim 2,wherein calculating transmission path loss and residual power in (ii)comprises adding the calculated transmission path loss and the residualpower in a storage unit and updating the same.
 7. The method of claim 6,wherein information on the added and updated transmission path loss andresidual power is stored in a software format, and deleted when apredetermined time period has passed.
 8. The method of claim 1, whereinrelaying the frame in the reverse direction of the unidirectional linkin (b) comprises setting residual power information and a relay requestfield in the frame.
 9. The method of claim 1, wherein a general frameprocessing method is performed when no relay request field is set in theframe or the destination of the frame is included in a neighboring nodelist in (b).
 10. The method of claim 8, wherein a general frameprocessing method is performed when no relay request field is set in theframe or the destination of the frame is included in a neighboring nodelist in (b).
 11. The method of claim 1, wherein removing the repeatedframe in (c) comprises: comparing residual power information included inthe frame with residual power information calculated at each mobilenode, and when the residual power information of the mobile node is lessthan the residual power information in the frame, removing thecorresponding frame.
 12. The method of claim 1, wherein providingunidirectional link connectivity in the link layer to an upper layer in(c) comprises: comparing residual power information included in theframe with residual power information calculated at each mobile node,and when the residual power information of the mobile node is greaterthan the residual power information in the frame, allowing the frame toreflect residual power information to a generation of back-off time sothat the mobile node with high residual power relays the correspondingframe in advance.
 13. The method of claim 1, wherein providingunidirectional link connectivity in the link layer to an upper layer in(c) comprises: providing the unidirectional link connectivity in thelink layer to the upper layer through a filtering process usingbroadcasting and residual power information.
 14. A recording mediumstoring a program including functions comprising: each mobile nodesensing a unidirectional link when a unidirectional link is generatedbecause of a difference between transmission powers, the mobile nodesforming a mobile ad hoc network; relaying a frame generated in a linklayer in the reverse direction of the unidirectional link when theunidirectional link is sensed; and removing the repeated frame relayfrom among the relayed frames, and providing unidirectional linkconnectivity in the link layer to an upper layer.